1. Field of the Invention
This invention pertains to the recordation of analog (or continuous) and digital (or discrete) information in a medium and, more particularly, to the recordation of images and/or data in the medium that are recoverable by the exposure of the medium to an illuminating light source.
2. Related Art
It is known in the art that a focused ion beam (FIB) apparatus can be used to alter selected regions on the surface of a medium, either by ion implantation into the medium, or by milling of the medium, and that the regions of implantation and/or milling can be controlled to within a spatial resolution in the nanometer (10−9 meters) range1. Micro-machining of materials can also be achieved by etch sensitization of the material, i.e. by using the fact that a region implanted with ions will etch at a different rate than the un-implanted region when exposed to strong acid or base solutions2. Furthermore, alteration of the medium by ion implantation has direct consequences to the optical properties (reflectivity, transmissivity, absorption,) of the materials3. In addition to material changes caused by implantation with ions, the optical properties of thin films has been well understood for many years4. Making use of the properties of optical thin films, it is possible to amplify small changes in optical properties of a material through the interference filtration properties of such optical thin films.    1. Watkins, R E J et.al., Focused Ion-Beam Milling, Vacuum, v. 36 961-967. 1986 Young, R J, Micromachining Using a Focused Ion Beam, Vacuum, v. 44 353-356. 1993    2. Choquette, K. D. et.al., Dry Lithography Using Focused Ion-Beam Implantation and Reactive Ion Etching of SiO2, Applied Physics Letters, 62, 3294-3296, 1993. Matiullah, Durrani, S. A., Measurement of the Etching Characteristics of Proton, Fission Fragment, and Heavy-Ion Tracks in CR-39, Nuclear Tracks and Radiation Measurements, 15, 203-206, 1988. Hosono, K. et.al., Novel Technique for Phase-shifting-mask Repair Using Focused-ion-beam Etch-back Process, Japanese Journal of Applied Physics part I, v. 31, 4468-4473. 1992    3. Townsend, P. D. et.al., Optical Effects of Ion Implantation, Cambridge Univ. Press, Cambridge, 1994.    4. Heavens, O. S., Optical Properties of Thin Solid Films, Butterworth's Scientific Publications, London, 1955. (reprinted by Dover Publications, Inc. N.Y. 1991)